Adjustable series resistance



Nov. 19, 1957 H. SCHELLING 2,813,955

. ADJUSTABLE SERIES RESISTANCE, ESPECIALLY FOR ELECTRO-MAGNETIC VEHICLE BRAKES 2 Sheets-Sheet 1 Filed March 25 v 1956 pi i/ iimnfi Nov. 19, 1957 SCHELLING 2,813,955

ADJUSTABLE SERIES RESISTANCE, ESPECIALLY FOR ELECTRO-MAGNETIC VEHICLE BRAKES Filed March 23, 1956 2 Sheets-Sheet 2 diii/j fi/j/ii a, 6 1 0 26 a ow D. MW 1 7. 2 2 2g my 1 a VY/Vlll l/VMY 1i: 1 w Q .l

p. a a i 2 in Wi /555555; Wilt 7Q .[F iM VVWfiM United States Patent Ofiice 2,813,955 Patented Nov. 19, 1957 ADJUSTABLE SERIES RESISTANCE, ESPECIALLY FOR ELECTRO-MAGNETIC VEHICLE BRAKES Hermann Schelliug, Winterthur, Switzerland, assignor to Albert Kuhn, Winterthur, Switzerland Application March 23, 1956, Serial No. 573,582 Claims priority, application Switzerland March 24, 1955 4 Claims. (Cl. 20148) The present invention refers to an adjustable series resistance, especially for electromagnetic vehicle brakes.

The adjustable series resistance according to the invention has a surround of contact strips, running parallel to each other and arranged in a circle, with the length of the strips, at one end, increasing between two limits from one strip to the next, contact springs movable along the strips and displaceable onto and off the separate strips, and a number of separate resistances corresponding to the number of strips, one end of these resistances being connected to a common terminal and the other end of each resistance being connected to a related one of the contact strips, and a ring carrying the contact springs and connected to another terminal, which ring is movable in the direction in which the contact strips extend to selectively engage the contact springs with the related contact strips.

In the accompanying drawing one example of execution of a series resistance according to the invention is illustrated, where:

Fig. 1 shows a side view of the series resistance with parts broken away,

Fig. 2 an axial section of the same and Fig. 3 a variant of a detail in axial section.

The series resistance as illustrated has a cylindrical insulating body 1, on whose periphery, running parallel to each other and to the axis of the cylindrical body 1, a surround of contact strips 2 is arranged. At the upper end, the strips 2 are in the same radial plane and have radially outward bent parts 3. The other end of the strips increases in length from strip to strip between two limiting values.

A contact spring 4 is movable on each of the strip 2. The contact springs 4 are fixed on a conducting ring 5 coaxial with the insulating body 1, and ring 5 is fixed to a ring 6 made of insulating material.

The described parts are arranged between two end Walls 7 and 8 and within a jacket 10 which is provided with apertures 9 and keeps the two end walls apart.

A central tube 11 extending from the lower end wall 7 passes through the insulating body 1, which is fixed firmly on the tube 11, whilst the insulating ring 6 is axially displaceable along the tube 11 by means of a sleeve 12.

Disposed around the tube 11, on a circle concentric with it, separate resistance bars 13 are arranged. These bars run parallel to the tube 11 and each consists of an insulating tube which carries a winding of resistance wire. The number of bars 13 is equal to the number of contact strips 2, and the electrical resistance of the resistance bars decreases from bar to bar between two limiting values. The resistance bar with the highest resistance is connected to the contact strip 2 with the greatest axial length, while the resistance bar with the next lower resistance is connected with the second-longest strip 2, and so on.

The connecting of the resistance bars 13 to the contact strips 2 is effected through their parts 3. The lower ends of the resistance bars 13 are connected to each other by a conducting ring 14, this ring 14 being attached to a ring 15 of insulating material which is fixed on the end plate 7. The terminal 16 is in electric connection with the ring 14. To another terminal 17, one end of a flexible cable 18 is fixed, while the other end of cable 18 is connected to ring 5.

In alignment with each contact strip 2 and electrically insulated from it, there is a strip 2, on which the free end of the respective contact spring 4 rests when in the state of rest (Figs. 1 and 2). The end of the strips 2 directed towards this strip 2' is chamfered (Fig. 2) and passes under a projection on the strip 2'. Because of this construction of the two strips 2 and 2', when the free ends of the springs 4 pass over from one strip to another in response to axial movement of the sleeve 12, the free ends of thecontact spring are radially displaced, so that the laying-on to and the taking-off from the strips 2 is efiected radially.

Two lever arms 19 are provided for displacing the ring 5 with the contact springs 4, so that the separate contact strips 2 and the separate resistances 12 connected to them are successively connected to the terminal 16 through the flexible cable 18. These lever arms 19, which can swivel about the pivot 20 on a part 21 screwed into the upper end of the tube 11, are connected through link 22 with a- I crosspin 23, which passes through a rod 24 axially adjustable in the part 21 and through an oblong slot 25 in the part 21. screwed, the head of the bolt 26 being received in a sleeve 27 displaceable in the tube 11. A crosspin 28 passes through the sleeve 27 and through an oblong slot 29 in the tube 11. A compression spring 30 is axially interposed between body 1 and ring 6 and, through the pin 28, the sleeve 12 and the ring 6, keeps the sleeve 27 in the position shown in Fig. 2, where the ring 5 and/or the contact springs 4 are not in contact with any of the contact strips 2.

When the lever arms 19 are swung in the direction of the arrows in Fig. 1; the rod 24 carries the sleeve 27 upwards by means of the bolt 26. By means of the pin 28 and the sleeve 12, the upwardly moved sleeve 27 raises the rings 5 and 6 and thus the contact springs 4.

In this manner the resistance bar 13 with the greatest resistance value is first of all connected between the terminals 16 and 17, and when the rings 5 and 6 move further upward the following resistance bars 13 are successively connected in parallel.

For adjusting the insulating ring 6 with the ring 5, a piston 31 is slidable axially in the tube 11 above a sealing sleeve 32. The piston 31 engages the sleeve 27 from below. When a fluid medium, for instance air or oil, is forced through a pipe 33 into a tube branch 34 on the underside of the end wall 7, the piston 31 moves upwards and, through the sleeve 27 and the pin 28, upwardly displaces the insulating ring 6 along with the ring 5. At the same time the switching-in of the resistance bars and/or their switching in parallel to each other is also eflected.

The parts 19 to 26 for eflecting movement of the ring 5 can be replaced by the arrangement illustrated in Fig. 3, wherein a part 35 is provided, which is screwed into the upper end of the tube 11 instead of the part 21. The part 35 has an axial bore receiving a wire 36 of a Bowden control cable encased in a flexible tube 37. The bolt 26 (Fig. 2) is screwed into a clamping sleeve 38 fixed at the end of the Wire 36. In other respects, the operation of the series resistance by means of the Bowden control cable is analogous to the operation of the parts 19 to 26 described above with reference to Figs. 1 and 2.

What is claimed is:

1. A series resistance especially for electromagnetic vehicle brakes, comprising a surround of contact strips, running parallel to each other and arranged in a circle,

Into the lower end of the rod 24 a bolt 26 is with the length of the strips, and one end, increasing between two limits from one strip to the next, contact springs movable along the strips and displaceable onto and off the related strips, a number of separate resistances corresponding to the number of strips, a first common terminal connected to one end of said separate resistances, means connecting the other end of each of said resistances to a related one of the contact strips, a ring carrying the contact springs, means connecting said ring to another terminal, said separate resistances being arranged parallel to each other distributed around the contact strips on a circle which is concentric to them, and an enclosing casing including two end Walls held apart from each other by a jacket having apertures therein.

2. A series resistance, especially for electromagnetic vehicle brakes, comprising a surround of contact strips, running parallel to each other and arranged in a circle, with the length of the strips, at one end, increasing be tween two limits from one strip to the next, contact springs movable along the strips and displaceable onto and ofi the related strips, a number of separate resistances corresponding to the number of strips, a common terminal connected to one end of said resistances, means connecting the other end of each of said resistances to a related one of the contact strips, a ring carrying the contact springs, means connecting said ring to another terminal, and a rest strip in alignment with each contact strip and having a projection overlapping the related contact strip.

3. A series resistance, especially for electromagnetic vehicle brakes, comprising a surround of contact strips, running parallel to each other and arranged in a circle, with the length of the strips, at one end, increasing be tween two limits from one strip to the next, contact springs movable along the strips and displaceable onto and oif the 2,813,955 a p P related strips, a number of separate resistances corresponding to the number of strips, a common terminal connected to one end of said resistances, means connecting the other end of each of said resistances to a related one of the contact strips, a ring carrying the contact springs, means connecting said ring to another terminal, and a rod connected to said ring carrying the contact springs and being spring urged in one direction so as to be movable in the direction opposed by the spring for adjusting the contact springs relative to the contact strips. 4. A series resistance, especially for electromagnetic vehicle brakes, comprising, a surround of contact strips, running parallel, to each other and arranged in a circle, with the length of the strips, at one end, increasing between two limits from one strip to the next, contact springs movable along the strips and displaceable onto and ofi the related strips, a number of separate resistances corresponding to the number of strips, a common terminal connected to said resistances, at one end of the latter, means connecting the other end of each of said resistances to a related one of the contactstrips, a ring carrying the contact springs, another terminal connected, to said ring, a piston, means connecting said piston to said ring, and means for applying a fluid under-pressure against said piston for adjusting the position of said ring, and of said contact springs thereon, relative to said contact strips.

References Cited in the tile of this patent UNITED STATES PATENTS 2,558,083 Green June 26, 1951 FOREIGN PATENTS 494,331 Germany Mar. 6, 1930 

